Network Working Group R. Earhart
Internet Draft: URL-SMTP Carnegie Mellon
Document: draft-earhart-url-smtp-00.txt December 1997
Expires June 1997
An SMTP URL Interface
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
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ftp.isi.edu (US West Coast).
This document suggests a proposed protocol for the Internet
community, and requests discussion and suggestions for improvements.
Distribution of this draft is unlimited.
The protocol discussed in this document is experimental and subject
to change. Persons planning on either implementing or using this
protocol are STRONGLY URGED to get in touch with the author before
embarking on such a project.
Abstract
It is occasionally useful to be able to reference a generic server to
be used for message submission. URLs provide a good mechanism for
refering to arbitrary network resources. The SMTP URL scheme allows
a URL to specify an SMTP server, thus allowing other protocols to use
a general ''URL to be used for message delivery'' in place of an
explicit reference to SMTP.
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Internet DRAFT An SMTP URL Interface December 15, 19971. Conventions Used in this Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [KEYWORDS].
2. SMTP URL Scheme
The SMTP URL follows the common Internet scheme syntax as defined in
[BASIC-URL] except that plaintext passwords are not permitted. If
:<port> is omitted, the port defaults to 25.
The specified server should not be assumed to have any services
available other than SMTP. Other than authentication, no protocol
actions are implied by an SMTP URL; an SMTP URL only specifies the
location of an SMTP service, not what to do with it (common actions
are to use the SMTP server to verify an address, and to submit
Internet mail).
An SMTP URL has the following general form:
url-smtp = "smtp://" url-server
"smtp" refers to the URL scheme; "://" is used to indicate a
reference to an Internet host address. The <url-server> element
includes the hostname, and optional user name, authentication
mechanism and port number.
Note that unsafe or reserved characters such as " " or "?" MUST be
hex encoded as described in the URL specification [BASIC-URL]. Hex
encoded octets are interpreted according to UTF-8 [UTF8].
3. SMTP URL User Name and Authentication Mechanism
A user name and/or authentication mechanism may be supplied. They
are used to perform SASL [SASL] authentication after making the
connection to the SMTP server. If no user name or authentication
mechanism is supplied, then the SASL ANONYMOUS [SASL-ANON] mechanism
is used by default. If an authentication mechanism is supplied
without a user name, then one SHOULD be obtained from the specified
mechanism or requested from the user as appropriate. If a user name
is supplied without an authentication mechanism then ";AUTH=*" is
assumed.
The ";AUTH=" authentication parameter is interpreted as described in
the IMAP URL Scheme [IMAP-URL].
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Internet DRAFT An SMTP URL Interface December 15, 1997
Note that if unsafe or reserved characters such as " " or ";" are
present in the user name or authentication mechanism, they MUST be
encoded as described in the URL specification [BASIC-URL].
4. Formal Syntax
The following syntax specification uses the augmented Backus-Naur
Form (BNF) notation as specified in [ABNF]. This uses the ABNF core
rules as specified in Appendix A of the ABNF specification [ABNF].
Except as noted otherwise, all alphabetic characters are case-
insensitive. The use of upper or lower case characters to define
token strings is for editorial clarity only. Implementations MUST
accept these strings in a case-insensitive fashion.
url-auth = ";AUTH=" ("*" / url-enc-auth)
url-achar = uchar / "&" / "=" / "~"
;; See [BASIC-URL] for definition of "uchar"
url-enc-auth = 1*url-achar
;; encoded version of auth-type-name above
url-enc-user = *url-achar
;; encoded version of login userid
url-server = [url-enc-user [url-auth] "@"] hostport
;; See [BASIC-URL] for definition of "hostport"
url-smtp = "smtp://" url-server
5. Security Considerations
SMTP URLs have the same security considerations as IMAP URLs [IMAP-
URL].
Clients SHOULD make the SMTP URL being used obvious to the user, as
using an undesireable server may compromise the security of the
user's message.
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Internet DRAFT An SMTP URL Interface December 15, 19976. Copyright
Copyright (C) The Internet Society 1997. All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
7. References
[ABNF] Crocker, Overell, "Augmented BNF for Syntax Specifications:
ABNF", RFC 2234, November 1997.
<url:ftp://ds.internic.net/rfc/rfc2234.txt>
[BASIC-URL] Berners-Lee, Masinter, McCahill, "Uniform Resource
Locators (URL)", RFC 1738, December 1994.
<url:ftp://ds.internic.net/rfc/rfc1738.txt>
[IMAP-URL] Newman, "IMAP URL Scheme", RFC 2192, July 1997.
<url:ftp://ds.internic.net/rfc/rfc2192.txt>
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